What’s deep beneath the sand at Camp Hero State Park in Montauk? Answers perhaps to a vast conspiracy theory that involves aliens, mind control, time travel, quantum wormholes, child abduction and the disappearance of an entire warship?

Northport native and filmmaker Christopher Garetano — who spent a considerable part of the last two decades digging into these questions if not actually into that sand — has produced a film, “The Dark Files,” which will air Friday on the History Channel at 10:03 p.m. Garetano and fellow Montauk sleuths Barry Eisler (author, former CIA operative) and Steve Volk (author of “Fringe-ology,” and a Philadelphia-based investigative reporter) head out to a place that has consumed conspiracists for decades. They poke in the sand. They find something.

Maybe.

I spoke with Garetano this week about his latest Montauk film. An edited transcript of our chat:

Where did you grow up and how did Camp Hero work its way into your life?

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I grew up in Northport, then went to the School of Visual Arts [in Manhattan], but I went out to Montauk when I was a kid.

So that’s when it all began?

I loved Montauk. It was a place where we spent summers and had a great time as a family. And then this strange thing happened and I would always ask questions about it. [The strange thing occurred when, as a 9-year old, he and his father saw a pair of large metallic spheres on the beach, and were told by a military official that they could not go any farther up the beach. The incident is relayed in tonight’s program.]

I saw the book (1992’s ‘The Montauk Project: Experiments in Time,” by Preston Nichols and Peter Moon) and wasn’t all that impressed by it. I already had a head filled with science fiction, everything from H.G. Wells to Philip K. Dick, and felt they were cherry-picking from a lot of things like ‘Twilight Zone’ or ‘The Outer Limits.’

Who changed your mind?

Al Bielek [who claimed to have been an early recruit to the so-called Montauk Project, which involved experiments in time travel and the rumored disappearance of that ship, the USS Eldridge; Bielek died in 2011]). To sit down with him and have him tell me it’s true was a great start.

You produced an earlier film, released in 2014, “Montauk Chronicles.” How is “The Dark Files” different?

There was interest from several networks in doing a program on [Camp Hero] and History finally ended up making it but [the production company] wanted to make something solid on the subject. They didn’t want to throw another two hours of conjecture at it. They wanted an investigation, and ‘The Dark Files’ is actually an investigation.

Obviously all the conspiracy theories hang on one key part of that conjecture — that underneath Camp Hero is a vast labyrinth of tunnels connecting various spaces where the so-called experiments were carried out. But the authorities never allowed you past the gates. What did you find under the ground and how did you find it?

Something extraordinary was found, which goes against all the official statements that there isn’t anything there. My co-hosts have a different perspective but my personal opinion is that this is a most significant find. There is something there and something very specifically that’s not natural.

Please do elaborate. Are there tunnels?

Yes, there are. We didn’t get into them but we have footage of them that was taken by someone else. But there’s something much more significant, much larger that you can see from the electric resistivity imagery tests we did.

They wouldn’t let us past the main gate so we insisted the engineers [operating the electrical resistivity tomography equipment] bring the equipment as close to the gate as possible. Stakes were set in the ground, and a current went up to 60 feet through the ground. [ERT is used to find subsurface structures, which can include tunnels or otherwise large spaces].

OK, what did the ERT find?

I’d rather viewers watch the special.

What do you personally believe happened at Camp Hero over all those years?

They were looking for human subjects and needed them for a variety of reasons. Let’s exclude aliens and time travel. This was about mind control, and these sorts of experiments have happened in other places too. There is a reason to believe that. [Famously, or infamously, the CIA’s covert ‘Project MKUltra’ — not conducted here — was a decades-long effort to develop torture procedures based, in part, on human experiments].

Any other Montauk projects on your horizon?

I’m in active development for a TV movie, a fictionalized account, based on this. Production starts in late December or early January.